In recent years, an electronic apparatus typified by a mobile phone or portable information terminal equipment is widely used, and the size reduction, reduction in weight, and prolonged service life of the electronic apparatus are strongly desired. Along with this, as a power source, a battery, particularly, a small-sized and light secondary battery that is capable of achieving a high energy density has been developed.
This secondary battery is recently considered to be applied not only to the above-mentioned electronic apparatus but also to various applications typified by an electric tool such as an electric drill, an electric vehicle such as an electric automobile, and a power storage system such as a power server for a house. As power sources of these apparatuses, a secondary battery having high output and a high capacity has been developed.
In the secondary battery, a liquid electrolyte (electrolyte solution), a gel electrolyte, or the like, is used. For example, Patent Literature 1 and Patent Literature 2 describe secondary batteries using gel electrolytes containing polyacrylonitrile.